What was Christian Huygens contributions to light?

Christian Huygens made significant contributions to the understanding of light, particularly through his wave theory. In his 1678 work, "Traité de la Lumière," he proposed that light travels in waves, introducing the concept of wavefronts and the principle of Huygens, which states that every point on a wavefront can be considered a source of secondary wavelets. This theory helped explain phenomena such as refraction and diffraction, laying the groundwork for later developments in optics. Huygens' ideas were foundational in the evolution of the wave theory of light, which eventually influenced future scientists like Thomas Young and Augustin-Jean Fresnel.